RU2118116C1 - Thermometer for measuring the temperature of body and method of measuring the patient's body temperature (variants) - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: first sensor of thermometer delivers signal of quantity of infrared radiation from surface of patient's tissue. Second sensor determines first sensor temperature. Processor connected to sensors processes output signals, determines temperature of body and transmits it to indicating facility. Processor contains many remembered coefficients corresponding to great number of temperatures of separate points. Processor provides for use of calibration distribution of multiple remembered coefficients for corresponding output signals during determination of temperature of body. Unit of probe head is directed alternately to great number of points, each point being maintained at corresponding standard temperature. Calibration distribution of great number of coefficients for every point is remembered. Then probe head unit is directed into external auditory channel, and temperature of body is determined. Temperature of body is also determined by selection of output signal of infrared radiation sensor on basis of maximum value of first and second sets of values. EFFECT: higher accuracy of temperature measurement. 21 cl, 9 dwg

Description

 The invention relates to measuring medical devices, more specifically, to a system and method for measuring the internal temperature of a human body by detecting and analyzing infrared radiation in the external auditory canal of a patient.

 The diagnosis and treatment of many diseases depends on the accurate reading of the temperature inside the patient’s body and, in some cases, on comparing it with previous indications. For many years, the most common way to measure patient temperature was to use mercury thermometers. They were sterilized, shaken, injected into the patient’s mouth or rectum for several minutes, then carefully checked visually to determine the height of the mercury column. Due to these inconveniences, electronic thermometers have been developed, and over the past 20 years they have become more widespread. The most successfully used oral thermometers. Such thermometers are sold under the trademarks IVAC and DIATEC. Usually they have a heat-conducting probe connected by wiring to a remote installation having an electronic circuit. The probe is placed in a protective free case before it is inserted into the patient’s mouth or rectum. Thanks to the use of advance technology, the temperature of the patient is measured in a very short period of time, for example 30 seconds, compared with the few minutes required for traditional mercury thermometers. Such electronic thermometers usually have measuring instruments or other displays that allow a specialist to determine the temperature faster than by studying the position of the end of the mercury column in a glass tube. Electronic thermometers of the aforementioned type may also provide in some cases more accurate temperature readings than mercury. Moreover, protective cases are needed so that the same thermometer can be used without autoclaving or another type of sterilization.

 The middle ear membrane is considered among doctors as a more suitable place for measuring the patient’s body temperature compared to the oral, rectal or axillary place, because it has a more pronounced property of reflecting body temperature or internal temperature and is more sensitive to changes in internal temperature. US patent N 3282106 Barisa proposed the possibility of using a tympanic thermometer, which could measure the temperature of the human body, taking infrared radiation in the external auditory canal. However, only when the system of US patent N 4602642 Gary J. O'Hara and others received a commercial basis under the federal registered trademark First Temp. Intelligent Medical Systems Inc. from Carlsbad, California, a clinically accurate tympanum thermometer has actually been introduced into clinical practice.

Clinical Thermometer First Temp. includes 3 components: a probe with an infrared sensor, a chopper for a given purpose, and a charging unit. In addition, controls are provided for preheating the IR sensor and the target to a reference temperature (36.5 ^o C) close to the temperature of the external auditory meatus, they are powered by the energy of the charging unit. The probe is usually mounted in a chopper where the infrared sensor and the target are preheated with heating controls. In this state, calibration is in progress. After that, the probe is separated from the interrupter and inserted into the external auditory meatus to detect infrared radiation from the eardrum. Measurement of body temperature is performed by comparing the detected infrared radiation with radiation from the target.

The accuracy of temperature measurement is achieved by the First Temp thermometer described above due to the described below. Various error factors are eliminated by pre-heating the probe with an infrared sensor and the target to a reference temperature (36.5 ^o C) close to normal body temperature, using heating controls. By heating the probe to a reference temperature that is higher than room temperature and maintaining the IR sensor at a constant temperature, despite the ambient temperature, the sensitivity changes of the IR sensor can be eliminated, and therefore, its error can be ignored. In addition, calibration is performed in such a way as to establish a reference target temperature close to the measured body temperature. Then, a comparative measurement is performed in such a way that the errors and errors associated with the characteristics of the optical system are reduced to a negligible level. Moreover, as soon as the probe is heated to a temperature close to body temperature, the problem of lowering the level in traditional measuring systems can be solved, i.e. the problem is that when a cold probe is inserted into the external auditory canal, the temperature in the external auditory canal and the temperature of the tympanic membrane decreases due to the probe, therefore, a correct measurement of body temperature cannot be achieved.

 The First Temp thermometer described above, presented in US Pat. No. 4,602,642, is an excellent instrument for measuring temperature accuracy. However, due to the fact that this thermometer requires a control heating system with high accuracy, its structure and circuits are complex and cause its high cost.

 In addition, it requires a relatively long stabilization period to preheat the probe and target and to control their temperature to a certain value. Moreover, the heating installation is powered by rather large batteries and requires a recharging installation connected to an AC source. Therefore, the use of the invention described in US patent N 4602642, it seems impractical in a portable clinical thermometer, operating on a small battery as a current source.

 Numerous attempts have been made to develop a portable tympanic thermometer that does not require heating to a specific value.

 U.S. Patent No. 4,797,840 to Freud, owned by THERMOSCAN, Inc. describes a thermometer that uses a pyroelectric sensor and therefore requires a portable shutter.

 US Patent No. 4,784,149 to Berman et al., Owned by OPTICAL SENSORS, describes an infrared tympanic thermometer that uses an unheated target whose temperature is detected during calibration.

 US Pat. No. 4,993,424 to Suszinski et al., Owned by DIATEK, Inc, describes a tympanic thermometer that requires a movable calibration plate.

 U.S. Patent Nos. 4993419 and 5012814 to Pompey et al., Owned by Exergen Corporation, describe a tympanic thermometer that goes on sale under the trademark OTOTEMP. The thermocouple is mounted inside a unitary heat sink, which runs along a tubular waveguide of variable cross-section. The length and reflectivity of the waveguide are controlled to limit the field of view of the thermocouple. It is assumed that the electronic circuit contributes to higher accuracy by determining the target temperature as a function of the temperature of the hot junction of the thermocouple, determined from the temperature of the cold junction and the known coefficient of the thermocouple. The determined internal temperature is controlled based on the ambient temperature with which the surface of the fabric is in contact.

 U.S. Patent No. 4,907,895 to Everest, owned by IVAC. CORP., Describes a tympanic thermometer that uses a gear wheel.

 U.S. Patent No. 5,017,018 to Yucci et al., Owned by NIPPON STEEL CORPORATION, describes another tympanic thermometer. Various tip designs are used to avoid errors associated with temperature changes within it, including a temperature sensor on the tip (FIG. 18).

 U.S. Patent No. 4,895,164 to Voula, owned by TELATEMP CORP., Describes a tympanic thermometer where a thermocouple and a thermistor that detects the temperature of a thermocouple are installed in close proximity to each other by means of an isothermal unit that significantly extends the distance around the waveguide.

U.S. Patent No. 5,024,533 to Egawa et al., Owned by Citizen Watch Co., describes a thermometer that uses a thermocouple 3a (Fig. 18) mounted in a metal housing 19 to receive infrared radiation from the external auditory canal through a tubular waveguide 20 made from a tube lined with gold. The radiation passes through the cap of a general type probe (sold by IMS) and through a silicon filter 2b. The first temperature-sensitive sensor 3b, which may be a diode, is placed in the housing 19 adjacent to the thermocouple 3a, for measuring the first thermocouple temperature and the ambient temperature. The second temperature sensor 3c is connected to the outer surface of the waveguide 20 to measure a second temperature of the waveguide. Using the layout diagrams shown in the functional diagram in Fig. 19, the third embodiment of the Citizen thermometer digitally displays the voltage of the first temperature sensor 3b and converts the voltage to degrees T ₀ . The circuit arrangement then shows the voltage in digital display of the second temperature sensor 3c and converts this voltage to degrees T _p . The circuit produces the following data embedded in it:
1) the sensitivity of the thermocouple at a known temperature;
2) the coefficient of change in sensitivity as a function of the temperature of the thermocouple;
3) gain of thermoelement amplifier;
4) thermocouple sensitivity based on the light receiving region of the sensor (field of view);
5) the temperature of the symmetrical axis to correct the throughput characteristics;
6) a conversion function that correlates the output signal of the environmental sensor to the temperature, in degrees;
7) a conversion function that correlates the output signal of the sensor with the optical waveguide to the temperature, in degrees;
8) the emissivity of the target (or taken equal to 1);
9) the emissivity of the optical waveguide.

 The circuit (FIG. 19) of a Citizen patent further shows the digital voltage value of the thermocouple 3a. It calculates the target temperature (i.e. body temperature) as a function of the stored sensitivity and radiation data. The circuit then corrects the set temperature using the inline correction data and ultimately corrects the set temperature as a function of the temperature difference between the ambient gray sensor and the waveguide sensor and the waveguide emissivity.

 The manufacture of block to block and the assembly of various parts located in the thermocouple, thermistors, and other components eliminates the need for a rigorous system of equations that describe the physical interactions of electronic and optical components to calculate body temperature with sufficient accuracy. Errors inevitable from each component accumulate and affect other elements. In known tympanic thermometers, each component must be calibrated separately. It is very difficult to determine the relationship between all components and a given temperature through a series of ambient temperatures. The experiments showed that sufficient accuracy is not achieved by using sensors to determine the temperature of the thermocouple and waveguide and subsequent processing of the signals in accordance with the equations that subtract a certain amount and the measured set temperature, which corresponds to temperature changes in the waveguide.

 Closest to the proposed invention in terms of the device and methods is a radiation clinical thermometer (US, 4832789, G 01 J 5/10, publ. 12.06.90) containing a first sensor for receiving a first output signal reflecting the amount of infrared radiation from the biological surface tissue of the patient, a second sensor for receiving a second output signal reflecting the temperature of the receiving means and the direction of infrared radiation, and a third sensor for receiving a third output signal reflecting the temperature of the receiving means and the direction of infrared radiation nation (Fig. 20), all sensors are connected to a processor that processes the output signals, the processing results are displayed on the display means.

 The method of operation of the thermometer consists in the fact that a preliminary temperature measurement is carried out by directing the tip of the probe to the reflective plate, while the measurement data is obtained from an infrared sensor, a heat-sensitive sensor for measuring the temperature of the probe, the obtained data are entered into a computer, and then the probe tip is inserted into external auditory canal, conduct a working temperature measurement based on data from the same sensors and calculate the temperature based on a software algorithm, taking into account Pipeline system of equations and the radiation density sensitivity coefficient and the temperature difference between the ambient temperature sensor and waveguide temperature sensor probe with the radiation coefficient of the waveguide. The final temperature value is displayed.

 The invention offers a very accurate method and apparatus for measuring human body temperature based on a new calibration technique that is independent of the system of equations and describes the connection of the components of the device in accordance with the physical laws of radiation.

 The device has sensory means for generating a first output signal representing a certain amount of infrared radiation reflected from the surface of the biological tissue of the patient. Further, the device has a second sensor for generating a second output signal representing the temperature of the first sensor. A processor coupled to the sensors processes the output signals to determine the patient’s body temperature using calibration targets for distributing the plurality of temperature points to the corresponding output signals. An indicator means connected to the processor provides the operator with data on a specific body temperature. In this case, the processor contains a plurality of stored coefficients corresponding to a plurality of target temperatures (calibration targets) and provides the use of a calibration distribution of a plurality of stored coefficients for the corresponding output signals in determining said body temperature.

 In addition, the thermometer contains means for receiving and directing infrared radiation, designed to receive infrared radiation emitted by the surface of biological tissue and directing radiation to the first sensor.

 The thermometer further comprises a third sensor connected to the processor to obtain a third output signal representing the temperature of the receiving means and the direction of the infrared radiation. Moreover, it contains an elongated waveguide, and the third sensor is thermally connected with it.

 In addition, the means for receiving and directing infrared radiation contains a hollow plastic probe surrounding the waveguide.

 Further, the processor is designed to determine the calibration distribution in a given range of ambient temperatures.

 The thermometer can also be a tympanic thermometer, its processor is designed to determine the calibration display in a given range of ambient temperatures, and the means for receiving and directing infrared radiation contains a probe with an elongated waveguide, and the third sensor is thermally connected to the probe.

 The thermometer indication means comprises a display. Further, the processor of the thermometer is designed to approximate the calibration distribution using an equation that uses many stored coefficients by performing multiple linear regression using the calibration distribution.

 The processor is also designed to determine the sequence of body temperatures in a given time interval and to select from it the maximum temperature of the type to be fed to the indicator means.

 In this case, the first sensor may contain a thermo column, and the second sensor is thermally connected with the first.

 The proposed method includes the steps of using a probe head block with a first sensor and a second sensor, receiving infrared radiation emitted into the ear canal of the patient, generating a first output signal representing the amount of infrared radiation incident on the first sensor, and forming using the second sensor, a second output signal representing the temperature of the first sensor, while the probe head block is sequentially directed to a plurality of targets (calibration targets), each of which is supported with a corresponding standard temperature, remember the set of coefficients corresponding to infrared radiation and the temperatures of the first and second sensors, respectively, which were obtained by sequentially directing the block of the probe head to many targets (calibration targets), remember the calibration distribution of the set of coefficients for each target, send the block of the probe head to external auditory meatus and determine the patient’s body temperature using the output signals of the sensors and the calibration distribution.

 Next, an equation is formed that approximates the calibration distribution, and the body temperature is determined by substituting the output signals of the sensors in the above equation.

 At the same time, a means of receiving and directing infrared radiation and a third sensor are used in the probe head block, while receiving and directing infrared radiation from the external auditory canal to the first sensor, a third output signal representing the temperature of the receiving and directing means is formed using a third sensor IR radiation, and include the values of the third signal for each of the goals in the calibration distribution.

 The probe head block is sent sequentially to a variety of ambient temperatures, and at each ambient temperature, the probe head block is sent sequentially to each of the many calibration targets, and they are also included in the calibration distribution of the values of the first and second output signals for each of the targets at each of the ambient temperatures .

 Further, it is possible to stabilize the probe head block at a first ambient temperature before being exposed to a second temperature, and a calibration distribution is formed during the time interval when the probe head block is cooled or heated to a second ambient temperature.

 A second embodiment of a method for determining a patient’s body temperature is also proposed, in which a probe tip is inserted into the patient’s external auditory meatus and an infrared radiation sensor, samples the output signal of the infrared sensor, samples the output signal of the infrared sensor radiation before the tip is inserted into the ear canal and the first set of values representing the signal is stored, then the probe tip is inserted into the external passage so that the infrared radiation in it gave the infrared radiation to the sensor, the output signal of the sensor is sampled and a second set of values representing this signal is stored, and the patient’s body temperature is determined based on the maximum value of the first and second sets of values.

 In FIG. 1a and 1b show a thermometer in an enlarged view (side view and longitudinal in cross section, respectively, are partially shown). Parts of a probe head kit that can be used in a preferred embodiment of the present invention. The mounted thermocouple detector is shown in vertical projection; in FIG. 2 is a functional block diagram of an electronic circuitry of a preferred embodiment; in FIG. 3 is a sequence diagram of all operations of a preferred embodiment; in FIG. 4 is a flow chart of steps performed by a preferred embodiment for determining body temperature; in FIG. 5 is a state diagram illustrating a menu reproduced during operation of a preferred embodiment; in FIG. 6 is a temperature chart in comparison with time, showing the property of looking ahead with a preferred embodiment; in FIG. 7 is an enlarged image of a pallet supporting several tympanic thermometers; in FIG. 8 is a diagrammatic illustration of a device used to calibrate a plurality of tympanic thermometers included in a preferred embodiment of the present invention; in FIG. 9 is an enlarged vertical view of some of the water-heated targets of the calibration apparatus shown in FIG. eight.

 The best way to implement the invention.

 There are two approaches to the design of the case of a tympanic thermometer, which consists of an infrared sensor and associated optics. The housing may be made of heat-conducting components (i.e., metal) in order to support all elements of the system isothermally. If the filters, the waveguide and the IR sensor are maintained at the same temperature, which is the so-called isothermal approach, the number of possible errors associated with changes in IR radiation from one of the above components will be significantly reduced. Unless electric heating is applied, this is not immediately achieved in a tympanic thermometer that comes in contact with an ear that has a different temperature than the sensor body. The isothermal design without active heating relies on all metal components or the high thermal conductivity of the components with close thermal contact. However, there are also temperature gradients. An alternative approach used in our invention is to design a housing using heat-insulating components (i.e. plastic) in order to reduce changes in the temperature of the filters, waveguide and IR sensor. This is the so-called non-isothermal approach.

 Turning to FIG. 1a and 1b. The presented embodiment of the present invention consists of a probe head block 8, which includes a first sensor in the form of a thermocouple (thermal column) 10. The first sensor is here referred to as an IR sensor. It produces a voltage corresponding to the temperature of the hot junctions relative to the cold junctions. A suitable thermocouple detector is sold by Dexter Research in Michigan. It consists of many individual thermocouples connected in series. Each thermocouple has a cold junction and a hot junction. See U.S. Patent No. 4,722,612 to Jankert et al. Of February 2, 1988. Thermocouple 10 produces a similar output signal (voltage) corresponding to a certain amount of infrared radiation that is incident on it. The presented embodiment of the present invention is intended for the perception of infrared radiation emitted by the surface of biological tissue, and in particular, the skin of the external auditory canal and the eardrum.

 The second sensor 12 (Fig. 1b) is connected to the thermocouple by means of a heat-conducting material Epoxy. It produces a similar output signal (voltage) on lines 12a representing the temperature of the thermocouple detector 10. For this purpose, one thermistor sensor is needed. Sensor 12 is here referred to as an environmental sensor, since it effectively measures the temperature of the room where the thermometer is used, and therefore the temperature of the thermocouple (thermocircle) 10. It is very important to know the temperature of the thermocouple when determining the amount of infrared radiation incident on it from its external signals.

 It is desirable that the first sensor has a fairly wide field of view, since the thermometer cannot change its orientation with respect to the ear. In other words, it is desirable to “integrate” the temperature of the ear canal and the eardrum than to obtain the temperature of one small point of the ear canal. A tubular waveguide placed nearby with an aperture of a visual image of a thermocouple will execute it. It is desirable that the waveguide be of the type Brass or Copper with a gold-plated inner diameter or to achieve the highest possible reflectivity of the infrared region of the spectrum, i.e. with a wavelength of 8 - 12 microns.

 As before, we turn to FIG. 1a and 1b. An elongated, usually cylindrical, hollow, plastic probe 14 surrounds and supports a waveguide in the form of a tube like Brass or Copper. The waveguide and the probe provide a method of receiving infrared radiation, directing to the thermocouple 10. The inner wall of the metal tube 16 is covered with a layer of gold 16a. The probe 14 has a tip 14a that is sized and configured to be inserted into the external auditory canal of the patient. The probe 14 consists of a rear portion 14 that is connected to the rear end of the intermediate portion 14c. The rear portion 14b and the intermediate portion 14c are enclosed in a plastic housing 15 (FIG. 1B). The housing 15 has a conveniently bent back part (not shown) for which the operator takes, the housing covers the bulk of the electronic components that make up the circuit shown in FIG. 2. The housing 15 is made of molded plastic AB. It is desirable that the probe 14 is also made of molded plastic AB, which has a low heat transfer coefficient.

 The rear end of the metal waveguide 16 is mounted inside a cylindrical stepped plastic mounted sleeve 17 (Fig. 1A) located inside the rear portion 14b of the probe. A plastic sleeve 18 surrounds and supports the front end of the waveguide tube. The outer diameter of the waveguide tube is smaller than the inner diameter of the intermediate portion 14c of the probe, which leads to the formation of an air gap G1 between them. This air gap minimizes the heat flux from the external auditory canal through the probe 14 to the waveguide 16. It is desirable that the air gap G be approximately 0.20 cm wide. The rear end of the waveguide tube is located at a distance of 0.012-0.02 cm from the thermocouple detector. This gap indicated in FIG. 1a and 1b as G2, prevents the passage of heat between them.

 The thermocouple detector 10 is mounted inside the rearwardly enlarged part of the sleeve 17 so that the active side of the thermocouple 19, equipped with a filter, receives infrared radiation transmitted down the waveguide 16. A plug made of molded plastic holds the thermocouple 10 inside the sleeve 17. The terminals 22 of the thermocouple pass through the holes plugs 20. A free hygienic body 23 in the form of a reflector (Fig. 1a) is mounted on the tip of the probe before it is inserted into the external auditory meatus of the patient. This reflector includes a transverse infrared-permeable membrane and means for removably attaching the membrane to the probe so that it protrudes through the tip 14a. The attachment means includes a tubular body 23b, which is deformed and latched onto the retaining protrusion 14c of the probe. See U.S. Patent No. 4,662,360 O'Hara et al. Of May 5, 1987.

 The plastic probe brought into contact with the ear and the combined waveguide will not quickly change the temperature. The tubular metal waveguide 16 will not have the same temperature as the reference junctions of the IR detector, and an error may occur if the waveguide reflectance is less than 100%. A reflectivity of 98% represents a predetermined practical limit on manufacturing limitations. Optical analysis showed that, on average, a beam of radioactive rays bounces 8 times inside the probe and the combined waveguide before it reaches the thermocouple. Therefore, the reflectivity is 0.988 or 85%. As a result, the emission of the waveguide 16 is 15%.

 The advantage of using a heat-conducting external probe 14 and an internal waveguide separated by an air gap is to minimize “lowering”, which is the outflow of heat from the ear as a result of contact with a heat-conducting object having a lower temperature than the ear. You can use a plastic probe with a metal sheathed layer as a waveguide. The advantage of a plastic waveguide is that, inserted into the ear, it does not change temperature quickly. However, the inconvenience of a plastic waveguide is that it is difficult to measure its temperature limit by a sensor mounted on it in one place, as will be explained later.

 An external filter 24 (Fig. 1) is attached to the front end of the probe 14. The filter 24 closes the front end of the waveguide 16, preventing dust and dirt from entering and thereby changing the reflectivity. Filter 24 should have the highest possible throughput in the infrared region with a passband equal to or wider than the passband on the thermocouple. For example, if the thermocouple filter has a passband of 8 to 12 μm along the wavelength, then the external filter 24 should have a wavelength in the passband of 8 to 12 μm or 7 to 13 μm. It is desirable that the permeability in the passband is 94%. Low transmittance values will increase the infrared radiation from the filter 24, which will cause an error associated with the heat from the ear, heating the filter in direct contact. One suitable filter 24 is made of germanium and has a multilayer, non-reflective coating on both sides. Such a filter is sold by Optical Coating Laboratories, Inc.

 The third sensor 26 (Fig. 1b) is thermally connected to the waveguide 16. This sensor generates a similar output signal (voltage) along the lines 26a representing the temperature of the waveguide 16. It is desirable that the sensor 26 be a thermistor connected by Epoxy. A line 26a from the thermistor extends through the air gap G and the groove 17a into the adapter sleeve 17. The third sensor is referred to here as the temperature sensor of the waveguide.

 The ejector sleeve 28 (Fig. 1a) surrounds the probe parts 14b and 14c, it can slide forward under the action of the spring S when manually pressing the ejector button (not shown) located on the housing 15. In order to engage the rear end of the reflector 24 and snap it off from the probe to be removed.

 FIG. 2 is a functional block diagram of an electronic circuit that can be used in a preferred embodiment of our invention. It includes a microcomputer 30, which receives operator commands through the control switch and configuration 32, and drives a display that controls the menu. By way of example, the microcomputer and the control menu display 34 may be presented as a single-chip HITACHI Model HD 4074808H and a liquid crystal display. The control and configuration switches may include a plurality of two-row pinout (DIP) switches that allow the operator to select a tympanic method, a method for measuring skin surface temperature, degrees Fahrenheit or centigrade, an oral measurement or an equivalent rectal measurement. Selector switches with similar functions are used in the aforementioned First Temp tympanometer.

 The work program executed by the microcomputer 30 may be recorded in an internal read-only memory (ROM) or EPROM of the microcomputer 30. Another storage device 36 is connected to the microcomputer to store the numerous algorithms used to determine the measured body temperature. As an example, this storage device may include an electrically erasable programmable read-only memory (EEPROM) with an IK bit, which is sold by ROHM. The signals from the sensors 10, 12 and 26 are conducted through a similar input and matching circuit 38. This circuit can be represented by the input chip of the Model N 74HC4051 multiplexer coming to the market from RCA. The signals from this circuit are passed through an analog-to-digital converter 40 to the microcomputer 30. This analog-to-digital converter (ADC) can be represented by a Model N TSC500 integrated circuit owned by TELEDYNE. It is desirable that the current source 42 be in the form of a 9 volt alkaline battery. The direct current from this source goes to the current regulator 44. This current regulator passes a positive 5-volt signal to the control element 46, which, in turn, is connected to the second current regulator 48 to provide a negative 5-volt signal. The current controller 44 may be in the form of an SC17710 YBA integrated circuit coming from SMOS. The current regulator 48 may be represented by a Model N TSC7660 integrated circuit coming from TELEDYNE. The control element 46 is able to turn off all and even reserve power when the thermometer enters the clock mode. The monitoring device may take the form of a simple field effect transistor (FET).

 Both a similar input matching circuitry 38 and an analog-to-digital converter 40 are connected to a reference voltage circuit 50 (FIG. 2). This voltage reference can be represented by the MC1403D integrated circuit from MOTOROLA. An external calibration device 52 may be coupled to the microcomputer 30 to calibrate the system. As will be explained later, in connection with the description of FIG. 7, this device includes an external computer that communicates with the microcomputer 30 through its internal I / O port. The sound signal 54 is controlled by a microcomputer to generate sound signals to predict operator actions or warn of other conditions, such as improper installation of a new hygiene cap or reflector on the probe or low power supply.

 The preferred embodiment of the thermometer of the present invention functions in a completely different way than previous infrared-sensitive thermometers that used a horizontal system of equations describing the relationships of components from the point of view of the physical laws of radiation, such as the Planck law and the Stefan-Boltzmann equations. Some of these thermometers corrected the obtained body temperature by subtracting the component associated with the temperature difference between the waveguide and the thermocouple.

The approach used in the present invention relies more on the field of integrated modeling systems than on radiation physics. After extensive experimental work, the applicant found that the relationship between all input signals and a given temperature is very difficult to determine. Instead, in the calibration process of a preferred embodiment of the present invention, a matrix is constructed representing a sufficient number of bindings of a given temperature and ambient temperature. Thus, the multidimensional surface is distributed in the form of a map, correlating the input signals to the measured output signals without taking into account the physics of the interaction between the input signals. For example, a predetermined temperature of 36.67 ^° C (C) may correspond to a thermocouple voltage of 31 μV, an ambient temperature sensor resistance of 1.234 Ohms, and an optical waveguide temperature sensor resistance of 4.321 Ohms. The output signal of 36.67 ^o C is the result of applying the distribution map of the three input signals to the temperature of a given absolutely black body. The preferred version of our thermometer does not determine what the ambient temperature, the temperature of the waveguide, or the sensitivity of the thermocouple are.

During the calibration process, the preferred embodiment of the thermometer of the present invention is as follows:
1) the thermometer is sequentially exposed to completely black dots, covering the range of its estimated radius of action;
2) the ambient temperature is repeated cyclically in the process of the above-mentioned exposure sequence by setting at various points covering the range of the estimated working radius;
3) for each given temperature, signals from a thermocouple, an ambient temperature sensor, an optical waveguide temperature sensor, and zero amplified values are accumulated;
4) in full, the entire set of input signals is superimposed on their output signals in accordance with the multiple linear regression technique. Various input data, apart from their square and cubic degrees, are independent variables compared to the target, which is a dependent variable;
5) the result of constructing the curve is a set of 13 coefficients that are used during measurement to determine the set temperature.

During measurement, the preferred embodiment of the thermometer according to the present invention:
1) shows 4 input voltages in digital display -
A) thermocouple (V _t );
B) the voltage of the ambient temperature sensor (V _a );
B) voltage of the waveguide temperature sensor (V _w );
D) zero amplified voltage (V _n ).

2) The set temperature T _{t is} calculated using the following algorithm with 13 coefficients (a ₁ -a ₁₃ ), which are determined during the calibration process:
T _t = a ₁ + a ₂ [V _t - V _n ] + a ₃ [V _t - V _n ] ² + a ₄ [V _t - V _n ] ³ + a ₅ V _a + a ₆ V $\genfrac{}{}{0ex}{}{\text{2}}{\text{a}}$ + a ₇ V $\genfrac{}{}{0ex}{}{\text{3}}{\text{a}}$ + a ₈ V _w + a ₉ V $\genfrac{}{}{0ex}{}{\text{2}}{\text{w}}$ + a ₁₀ V $\genfrac{}{}{0ex}{}{\text{3}}{\text{w}}$ + a ₁₁ [V _t - V _n - V _a ] + a ₁₂ [V _t - V _n - V _a ] ² + a ₁₃ [V _t - V _n - V _a ] ³ .

The square and cubic terms of the algorithm given above lead to the fact that some members of the equation become very large, while others become very small in relation to each other. The preferred embodiment of our thermometer uses a small microprocessor with limited program memory, limited super-operative memory, limited memory for storing constant values, and limited data processing speed. In order to optimize the reserves of this relatively small microprocessor, large differences in the relative values of the terms in the algorithm using the number of floating point numbers are best adapted. Such numbers have two parts: exponent and mantissa. Mantissa requires the most bits. In order for a relatively small microprocessor to calculate body temperature using the above algorithm most efficiently, the value of the mantissa of floating-point numbers should be limited. Limiting the size of the mantissa saves program memory when copying arithmetic operations, saves super-operative memory and saves the size of read-only memory, since there are fewer numbers, and saves processing time, since fewer bits are processed. However, when the number of bits in the mantissa is reduced, some accuracy is lost when a large number is added to a small number, due to a reset error. In order to keep this error within acceptable limits, the difference in the value of the numbers added together must be kept within limited limits. Although not shown in a predefined algorithm of 13 coefficients, the applicant found that by adding a constant, here referred to as “offset” to one or more members in the regression, the coefficients of the algorithm can be changed without affecting the accuracy of the result, and at the same time it decreases discard error. When you select this constant "offset" is a number of trial regressions. Then it is necessary to determine at which set of coefficients there will be the least errors when resetting. Two solutions are possible. First of all, the number of test calculations can be performed with the selected microprocessor or a method of emulating software and hardware in relation to the package and for performing floating-point operations of the selected microprocessor. An alternative approach is to determine which set of coefficients gives the best results when studying the coefficients themselves. This latter approach is most desirable, since it requires little time and costs to ensure it. To make this second approach effective, a proof or statistical drop calculation is required. The applicant has developed a statistical calculation that can be obtained from the ratio of the coefficients. The ratio he developed has the form
T _stat = a ₁ + a ₂ (a ₃ + a ₅ ) a ₆ + a ₈ (a ₉ - a ₁₁ ) a ₁₂ .

Then the regression with the lowest value of T _stat is selected as the most optimal, which gives the least errors when discarding.

 Determining the degree of thermal equilibrium between the thermocouple and the waveguide is not possible with the preferred embodiment of the thermometer according to the present invention. This is because neither the sensor associated with the thermocouple, nor the sensor associated with the waveguide, are calibrated with the thermocouple, nor the sensor associated with the waveguide are calibrated with respect to each other or to any temperature scale. Therefore, the preferred embodiment of the thermometer of the present invention cannot determine to what extent any sensors are in equilibrium with each other either by calibration time or by temperature measurement time. Such a determination is not necessary with the method for determining body temperature from infrared radiation according to the present invention.

 In a preferred embodiment of the thermometer of the present invention, there is no means or adjustment of the electrical signal from the infrared sensor. The correction concept is not applicable to the calibration or measurement method of our invention. All sensor output data is distributed on the map to give the set temperature in accordance with the thirteen-dimensional surface map, which was determined during calibration. No sensor input is used to correct any other input signal / s. The intermediate (uncorrected) temperature is not determined.

 At an early stage in the development of the thermometer of the present invention, an adjustment technique was tested using an approach to adjusting known inventions to the temperature difference between the thermocouple and the waveguide. However, the applicant rejected this approach because of the inability to make adjustments in a sufficient range of conditions and the unacceptable accumulation of tolerances of the individual components. This problem suggested a radically different approach arising from the subject of the present invention.

 In FIG. 3 is a general structural diagram of an operation of a first embodiment of a tympanic thermometer of the present invention; in FIG. 4 is a flowchart of steps performed by a preferred embodiment for determining body temperature.

A preferred embodiment of the thermometer of the present invention also includes a “forward looking” feature. The duration between the insertion of the probe 14 into the external auditory canal and the pressing of the SCAN button may vary depending on the operators. Due to the lowering effect, this difference between the operator may be the result of different measured temperatures. Turning to the graph of FIG. 6, it can be understood that lowering the level prevents a “flat” waveform. If the operator presses the SCAN button after lowering the condition reduces the test temperature, the peak temperature value will be lost. As indicated above, the solution is to start sampling the output of the thermocouple at T _at when the probe cap or reflector is initially mounted on the tips of the probe 14a. Samples can be stored in a one second ring list. When the SCAN button is pressed, fetching the fuser output signal continues for another second. The microprocessor 30 then selects a peak value from two second samples. The first interval of one second before pressing the SCAN button is presented as T _in - t ₁ . The second interval of one second is represented as t ₁ - t _E.

Turning to FIG. 4. The instruments described below reflect the installation of a reflector or probe cap on the thermometer. The microprocessor 30 receives a signal indicating that the cap is on the probe. Then the microcomputer starts sampling the output of the thermocouple at a speed of 16 samples per second. The values in the digital display of the similar thermocouple output signals are recorded in a ring list. As soon as the thermometer button is pressed, the microcomputer starts sampling the output signal of the thermocouple 14 times, and then the output signal of the environmental sensor and the waveguide sensor separately and stores the values in the digital display of these output signals. In addition, the microcomputer selects the zero amplified voltage value (V _n ) and stores its digital value. The microcomputer then looks at the annular preview list and the postview list to search for the peak output of the thermocouple. Using the digital value of this peak output signal of the thermocouple together with the digital values of the output signals of the second and third sensors and zero amplified voltage, the body temperature is calculated using the previously described algorithm, which was caused by multiple linear regression performed on calibration targets.

 The reed switch 56 (FIG. 1 a) on the printed circuit board 58 is driven by a magnet 59 mounted in the ejector sleeve 28 with a reciprocating motion. A printed circuit board is mounted on the rear end of the probe portion 14b. When the reflector 23 is mounted on the tip of the probe 14a, its rear end engages the front end of the sleeve 28 and pulls it so that the spring S is compressed. As a result, the magnet 59 moves away from the reed switch 56, sending a signal to the circuit of FIG. 2, which lets the microprocessor 30 know that the reflector is installed. This forces the microprocessor to start sampling at a speed of 16 per second.

During the mass production of the thermometers of the aforementioned type, they must be calibrated in a complete set. In FIG. 7 is an enlarged view of a pallet 60 on which a plurality of tympanic thermometers 61 are mounted, 3 in a group. The probe of each thermometer is directed down into the corresponding hole (not visible) in the pallet. FIG. 8 is a diagram of an apparatus used to calibrate a plurality of tympanic thermometers according to a preferred embodiment of the present invention. Many pallets with thermometers are placed in a climatron 62, tuned to a first predetermined ambient temperature. One such test chamber is the CYBORTRONICS 3000 Series Camera. CYBORTRONICS Inc. From Irwin, California. Test bench 63 is located in the center of the climatron. The stand contains 4 sets of 64, 66, 68 and 70 three targets of absolutely black bodies, which are at exact temperatures of 29.44 ^o , 35 ^o , 38.88 ^o and 43.33 ^o (C). The water flowing through the targets of completely black bodies serves to accurately maintain their temperatures, as will be described in more detail below. Water flows back and forth to each of the 4 sets through separate pipes 72, 74, 76 and 78. These individual water lines are shown in the diagram with one line 80, showing the corresponding temperature controlled pumping units 82, 84, 86 and 88. One of these pumping units is represented by a TEMPETTE TE-8D unit from Techne Ltd from California, England.

 It is desirable that the personal computer with the INTEL 486 microprocessor is compatible with the external computer 90 (Fig. 8), which receives signals from the test bench 62 depending on the temperature of the sets of 64, 66, 68, and 70 targets of completely black bodies. Turning to FIG. 9. Each set of goals of absolutely black bodies. Turning to FIG. 9. Each set of targets of completely black bodies, such as 64, consists of a cylindrical hollow vessel 92 connected in line with a corresponding separate waveguide, such as 72. Three cylindrical sockets 94, 96 and 98 open outward through corresponding openings in the side of the vessel 92 and have a sealed bottom shown in FIG. 9 with a dashed line. The tips of the respective thermometer probes are calibrated down into these cylindrical sockets made of black anodized aluminum. Thus, the nests play the role of given absolutely black bodies. The thermistors 100, 102, and 104 are securely connected through the heat conductivity of the epoxy material to the walls of the sockets 94, 96, and 98. The terminals 100a, 102a, and 104a of these thermistors are connected to the corresponding digital-to-analog converters, which are together marked in FIG. 8 is the number 106.

Many pallets 56, each of which has 12 thermometers 61, are installed inside the climatron at a selected ambient temperature, that is, 15.56 ^o C. The pallet can then be manually installed on a stand 108 in the center of the test bench 62. This is done by the operator, entering the chamber through gloved portals located in its side wall. The pallet has such a configuration that the tip of each of the thermometers is directed inside the corresponding socket, belonging to it a set of a given absolute black body. Each of the thermometers is connected to the control computer 90 by means of one of the corresponding 12 consecutive terminals represented by line 110 in FIG. 8 and by means of an electrical wiring diagram and connection block, indicated by 112 in the diagram. The base 108 can be rotated in 90 ^° increments using a motor (not shown) to sequentially direct the tip of each thermometer to predetermined absolutely black bodies that are maintained at a temperature of 29 , 44 ^o, 35 ^{o, o} 38.88 and 43,33 ^o C. The computer controls the rotation of the circular track 60 and the pallet thus indicates on what purpose the thermometer through the switch circuit 114 denoted by line 116. This occurs at each Rotating pallet 90 ^o 60.

The output from the microcomputer 30 of each thermometer, representing the signals from the sensors 10, 12 and 26, is sent to an external computer 90, indicated by line 110, and recorded by memory 118, which can take the form of a Winchester-type drive. Calibration is controlled by the operator using the data entered from the keyboard and the CRT display 120. This process is repeated at an ambient temperature of 21.11 ^o , 26.67 ^o , 32.22 ^o and 37.78 ^o C inside the climatron.

Typically, a calibration distribution is performed in a way that mimics a changing ambient temperature, for example, a climatron can be adjusted to 15.56 ^o C. A pallet with 12 thermometers can be left to stabilize at room temperature at 21.11 ^o C. Then the pallet can be placed on a test bench inside the climatron and the output signals of the sensors can be recorded as the pallet rotates over a given absolutely black body for a time while the thermometers are cooled to a temperature of 15.56 ^o C.

 Once all the data is collected and stored in memory 118, an equation is drawn up using the regression described above, which gives approximate values for the calibration distribution of the map of each thermometer. The coefficients of each member of the equation are recorded in the memory 36 of the corresponding thermometer.

 Applicant has found that it is possible to improve map distribution by adding information about the history of the sensors with respect to the regression input signals. This is especially true for a thermocouple. The output of the thermocouple is proportional not only to the environment at the moment, but also to the environment in the recent past. Regression can be clarified by adding a few additional members that contain information about the sensor’s background: TPIIAD (t-1), TPIIAD (t-2). TPIIAD (t-3), TPIIAD (t-4) ... where TPIIAD (t-1) - represents the thermocouple sensor reading one time back, TPIIAD (t-2) - two time back, TPIIAD (t-3 ) - three time periods ago, etc. The time intervals can be seconds or multiple numbers, or their test numbers, depending on the time constant of the sensor. Square and cubic forms of the above parameters can be included in order to further clarify the calibration distribution of the card in cases where the cards with straight lines are insufficient.

 There are other ways to describe a story that may have the same result. For example, instead of using the sensor output signal in time t-1, t-2, etc. one or more low-pass filters can be applied to integrate the sensor output. The first and possibly second derivative of the sensor output can be used to determine the rate of exchange of the sensor. These parameters, alone or in combination with the sensor output signals at time t-1, t-2, etc. can be used to refine the distribution map.

In the description of the preferred embodiment of the tympanic infrared thermometer and the method for measuring body temperature according to the present invention, it should be clear that various modifications and adaptations can be made by specialists. For example, thermistors 12 and 26 can be replaced with other temperature sensors with a faster time constant, including diodes, RTD, thermocouples, or integrated circuits. The coefficients of the equation that refine the distribution can be determined by numerical approximation, multiple regression, or another method of “fitting” the curve. Instead of calculating the body temperature using the written equation, a conversion table can be used. The third sensor on the waveguide can be removed, although the result the degree of accuracy can be reduced, and this inaccuracy can be minimized by actively heating the optical head kit or by reducing the level reduction that sometimes occurs. chaetsya during insertion of the probe tip into the external ear canal. Working program can be composed based offset correction to output specific data about body temperature on the screen to change to equalize room temperature from a nominal room temperature of, for example 21,11 ^o C, as shown environmental sensor 12. The amount of bias correction may be a function of the measured ambient temperature rather than a fixed bias. Therefore, the scope of patent protection of the present invention is determined by the formula from Bretenoux.

Claims (1)

 \\\ 1 1. A thermometer for measuring body temperature, comprising a first sensor for receiving a first output signal representing the amount of infrared radiation from the surface of the biological tissue of the patient, a second sensor for receiving a second output signal representing the temperature of the first sensor, a processor connected to the sensors, for processing the output signals and determining the patient’s body temperature and indicating means connected to the processor, for presenting to the user an indication of the obtained body temperature, characterized in that the processor contains a plurality of stored coefficients corresponding to a plurality of target temperatures (calibration targets), and enables the use of a calibration distribution of a plurality of stored coefficients for corresponding output signals in determining said body temperature. \\\ 2 2. The thermometer according to claim 1, characterized in that it contains means for receiving and directing infrared radiation, intended for receiving infrared radiation emitted by the surface of biological tissue, and directing radiation to the first sensor. \\\ 2 3. The thermometer according to claim 2, characterized in that it contains a third sensor connected to the processor to obtain a third output signal representing the temperature of the receiving means and the direction of infrared radiation. \\\ 2 4. The thermometer according to claim 3, characterized in that the means for receiving and directing infrared radiation contains an elongated waveguide, the third sensor being thermally connected to the waveguide. \\\ 2 5. The thermometer according to claim 4, characterized in that the means for receiving and directing infrared radiation contains a full plastic probe surrounding the waveguide. \\\ 2 6. Thermometer according to any one of claims 1 to 5, characterized in that the processor is designed to determine the said calibration distribution in a given range of ambient temperatures. \\\ 2 7. The thermometer according to claim 3, characterized in that it is a tympanic thermometer, the processor is designed to determine the calibration display in a given range of ambient temperatures, and the means for receiving and directing infrared radiation contains a probe. \\\ 2 8. The thermometer according to claim 7, characterized in that the probe contains an elongated waveguide. \\\ 2 9. The thermometer according to claim 7 or 8, characterized in that the third sensor is thermally connected to the probe. \\\ 2 10. The thermometer according to any one of claims 1 to 9, characterized in that the indicating means comprises a display. \\\ 2 11. The thermometer according to any one of claims 1 to 10, characterized in that the processor is designed to approximate the calibration distribution by means of a control using a plurality of stored coefficients. \\\ 2 12. The thermometer according to claim 11, characterized in that the processor is designed to obtain an equation by performing multiple linear regression using a calibration distribution. \\\ 2 13. A thermometer according to any one of claims 1 to 12, characterized in that the processor is designed to determine the sequence of body temperatures in a given time interval and to select from it the maximum body temperature for supply to the indicator means. \\\ 2 14. The thermometer according to any one of claims 1 to 13, characterized in that the first sensor comprises a temperature column. \\\ 2 15. The thermometer according to any one of claims 1 to 14, characterized in that the second sensor is thermally connected to the first sensor. \\\ 2 16. A method for determining a patient’s body temperature, in which a probe head unit with a first sensor and a second sensor is used, infrared radiation received in the patient’s ear canal is received, a first output signal representing the amount of infrared radiation incident on the first sensor is formed, and form using a second sensor a second output signal representing the temperature of the first sensor, characterized in that the probe head block is sequentially directed to a plurality of targets (calibration targets), each of which the temperature is maintained at the corresponding reference temperature, a plurality of coefficients corresponding to infrared radiation and the temperatures of the first and second sensors, respectively, which were obtained by sequentially directing the probe head block to a plurality of targets (calibration targets) are stored, the calibration distribution of the plurality of coefficients for each target (calibration target), direct the probe head block into the external auditory canal and determine the patient’s body temperature using the sensor output signals and the calibration distribution. \\\ 2 17. The method according to clause 16, characterized in that they form an equation that approximates the calibration distribution, and determine the body temperature by substituting the output signals of the sensors in the above equation. \\\ 2 18. The method according to item 16 or 17, characterized in that in the block of the probe head use means for receiving and directing infrared radiation and a third sensor, while receiving and directing infrared radiation from the external auditory canal to the first sensor, form using the third sensor, the third output signal representing the temperature of the receiving means and the direction of infrared radiation, and include the values of the third signal for each of the targets (calibration targets) in the calibration distribution. \\\ 2 19. The method according to any one of paragraphs. 16 - 18, characterized in that they hold the probe head block sequentially at a variety of ambient temperatures and, at each ambient temperature, send the probe head block sequentially to each of the many targets (calibration targets), and also include in the calibration distribution the values of the first and second output signals for each of the targets (calibration targets) at each of the ambient temperatures. \\\ 2 20. The method according to any one of paragraphs.16 to 19, characterized in that the probe head block is stabilized at a first ambient temperature before being exposed to a second ambient temperature, and a calibration distribution is formed during the time interval when the head block the probe is cooled or heated to a second ambient temperature. \\ \ 2 21. A method for determining the patient’s body temperature, in which a probe tip is inserted into the patient’s external auditory meatus and an infrared radiation sensor in the probe head block, the output signal of the infrared radiation sensor is sampled before the probe tip is inserted into the external auditory meatus and the first set of values representing the said signal is stored, the probe tip is inserted into the external passage so that infrared radiation in the external auditory canal falls on the infrared radiation sensor, sampling the output signal of the infrared sensor and storing a second set of values representing this signal, characterized in that the patient’s body temperature is determined based on the maximum value of the first and second sets of values.

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